1. Field of the Invention
This invention relates to roll casting of metal, such as aluminum. More particularly, this invention relates to side edge dam means for roll casting which restrain the edges of the metal, as it is cast, without necessarily physically contacting the metal.
2. Description of the Prior Art
In roll casting apparatus, a nozzle tip is located adjacent to the nip of a pair of rollers to deliver a stream of molten metal to the rollers. Particular improvements in such apparatus are described and claimed in pending Ai et al Ser. Nos. 597,834 and 597,835; and Yu et al Ser. Nos. 597,911 and 597,912; all assigned to the assignee of this invention, and cross-reference to which is hereby made.
The usual practice in such roll casting apparatus is to provide stationary side edge dams adjacent the exit of the nozzle to retain the edge of the molten metal flow as it enters the rollers. In the use of this type of "contacting" edge dam, the amount of contact varies with the casting conditions. However, when contact does occur, rough or ragged sheet edges can result from this contact.
A number of prior art patents have addressed the problem of containing or shaping the flow of molten metal in a non-contacting manner using electromagnetic field means. Typical of such patents are U.S. Pat. Nos. 4,020,890; 4,353,408; 4,358,416; 4,375,234; 4,419,177: 4,461,338; and 4,471,832; and British Patent No. 1,529,731.
Wood et al U.S. Pat. No. 4,367,783 discloses the use of side edge dams which may be urged against the metal either by springs or hydraulic means under the control of a pressure sensing load cell means.
European Patent Application No. 0,071,802, published Feb. 16, 1983 discloses the use of a combination of electromagnetic and pneumatic means to seal the gap between a casting nozzle tip and upper and lower casting belts in an apparatus having solid side walls.
There remains, however, a need to provide means for essential non-contacting containment of the side edges of the molten and/or solid metal during casting which will be relatively simple and inexpensive, and yet possess the flexibility to permit changing the width of the material being cast "on the fly", i.e., as the metal is being cast. This, of course, effectively precludes the use of expensive and stationary electromagnetic field generating means.